Question

A and B can do a work in 40 days, B and C in 10 days, C and A in 8 days. If A, B and C work together, they will complete the work in?

• A. 10 days
• B. 47/6 days
• C. 7.5 days
• D. 47/3 days
• E. $8days$

Answer 1

The correct option is E

$8days$

(A + B)'s 1 days work $=\frac{1}{40}$; (B + C)'s 1 days work $=\frac{1}{10}$; (A + C)'s 1 day's work $=\frac{1}{8}$
Adding, we get : 2 (A + B + C)'s 1 day's work $=(\frac{1}{40}+\frac{1}{10}+\frac{1}{8})=\frac{10}{40}=\frac{1}{4}$
$\therefore$ (A + B + C)'s 1 days work $=\frac{1}{8}$
So, A, B and C together can complete the work in 8 days.